RU2591182C1 - Method for compensation of induced voltage in operating site on overhead transmission line at short circuit at operating line - Google Patents

Abstract

FIELD: electronic equipment.

SUBSTANCE: according to method at work place phase conductor wires of disconnected line are connected by earthing into a star, which centre is connected with line support grounding circuit by ground wire. Value of current induced voltage on the disconnected line at short circuit at operating line is predetermined, by value of which a capacitor battery power of independent current source is formed, which is permanently charged from autonomous source of electric energy. In production of work current is measured in wire connecting star grounding wires with grounding circuit of line support, by value of which control action in control unit is formed in real time, which is supplied to unit for generating compensating current, at outlet of which, using a charging capacity of capacitor bank installed instantaneous current equal in value and being in antiphase to measured current is fed compensating current in conductor connecting star grounding wires with grounding circuit line support and controlled residual induced voltage not exceeding 25 V.

EFFECT: higher safety of works in electrical installations by reduction of induced voltage in place of production works.

1 cl, 4 dwg

Description

The present invention relates to the electric power industry and can be used to provide safety measures during operations on disconnected overhead power lines, on which additional voltage is induced from neighboring operating lines, including in the event of short circuits on operating lines.

The claimed invention relates to a priority area of development of science and technology "Technologies for creating energy-saving systems of transportation, distribution of heat and electricity" [Alphabetical subject index to the International Patent Classification in priority areas of science and technology / Yu.G. Smirnov, E.V. Skidanova, S.A. Krasnov. - M.: PATENT, 2008 .-- p. 97].

Electrical installation rules [PUE, Approved by the Ministry of Energy of the Russian Federation, order No. 204 of July 8, 2002] when operating electrical installations, security measures were determined during operations on overhead power transmission lines, on which additional voltage is induced from neighboring operating lines. Safety measures were separately highlighted when working on such lines when grounding them in accordance with the general requirements of the rules does not allow lowering the potential induced on the disconnected wires below 25 V. In accordance with the rules, a list of lines that are switched off under induced voltage is formed. The list includes overhead lines (their sections), the induced voltage value of which exceeds 25 V, as well as overhead lines built on double-circuit (multi-circuit) supports. The induced voltage values are obtained using a simplified calculation method or line measurements.

At the same time, no safety measures were identified during operations on overhead power lines, on which additional voltage is induced from neighboring operating lines during short circuits on operating lines, when the induced voltage during the short circuit can reach hundreds of volts, which creates a high probability of a life threat working.

It is known that on any overhead line running in parallel with other overhead lines, a third-party potential is continuously induced, due to the mutual influence of the electromagnetic fields of these lines on each other. The potential value depends on the operating voltage, load currents, the distance between the phase conductors of the lines and the length of the section parallel to their location. The potential induced on each of these lines (induced voltage) can be arbitrarily represented as the sum of two components: electrostatic and electromagnetic.

A known method of reducing the inductive effect of AC networks on wired communication communications [patent RU No. 2298487, IPC B60M 1/06, B60M 3/00 (2006.01), publ. 05/10/2007], in which an additional adjustable source of compensating voltage is used, which is in antiphase to the supply (to induced) voltage. An additional adjustable source of compensating voltage is connected to an additional wire located parallel to the communication wires, grounded on one side. As a result of the addition of the electric fields of the supply (induced) voltage and the source of the compensating voltage, the electric effect of the network on adjacent wire communication lines is reduced to almost zero.

Signs of an analogue that coincide with the essential features of the proposed method is the connection of an adjustable source of compensating voltage to the ground loop through an additional wire located parallel to the communication wires.

In this method, only the electrical component of the induced voltage is compensated and the electromagnetic component is not affected, which does not exclude the appearance of the induced voltage from the electromagnetic component.

A known method of reducing the electromagnetic effects of electric networks of railways on wire communication channels [Auth. testimonial. No. 1400922 dated 12.12.1988, IPC V60M 1/06, Bull. No. 35 dated 09/23/1991]. In this method, the obtained traction current signal is phase shifted by 180 ° electrical, amplified to the required level and fed through the current source to the protective conductor.

In this method, only the electromagnetic component of the induced voltage is compensated and the electrical component is not affected, which does not exclude the appearance of the induced voltage from the electrostatic component.

It is a well-known way to reduce the induced voltage by grounding the phase wires of the disconnected line at the place of work, [PUE, Approved by the Ministry of Energy of the Russian Federation, order No. 204 of July 8, 2002]. The electrostatic component of the induced voltage on the wires of the disconnected overhead line is due to the influence of the electric field on them of the adjacent (influencing) line remaining in operation and depends only on the voltage level of the influencing line. The value of this component is the same along the entire length of the disconnected overhead line. The electrostatic component of the induced voltage decreases to a safe level along the entire length of the line when it is grounded at any, at least one point. Therefore, the impact of this component is completely eliminated by grounding the disconnected overhead line at the ends (at substations) and at the place of work. The electromagnetic component of the induced voltage is due to the total influence of the magnetic fields generated by the currents of the phase wires of the influencing line. A feature of the manifestation of the electromagnetic component of the induced voltage is the invariability of its value, regardless of whether the wire is isolated from earth or grounded in one or even in several places.

A known method of compensating induced voltage [patent RU No. 2541508], adopted as a prototype, in which ground wires connect the phase wires of the disconnected line to the ground loop of the line support at the place of work, pre-determine the power of the induced voltage source, form an autonomous power source with the ability to control the magnitude and the phases of the compensating voltage, measure the magnitude of the induced voltage at the place of work with a voltmeter, connect between the ground loop tions support lines and grounding conductors steering power source, which sets a voltage equal in magnitude and being in phase opposition to the measured induced voltage, and control the value of the voltmeter residual induced voltage not exceeding 25 V.

The signs of the prototype, which coincide with the essential features of the proposed method, are as follows: connect the phase conductors of the disconnected line with ground wires to the ground circuit of the line support at the place of work, pre-determine the power of the induced voltage source, form an autonomous power source, connect the line supports and ground wires between the ground circuit adjustable power source, control according to the voltmeter readings the value of the residual induced voltage, not exceeding 2 5 V.

The method proposed by the prototype allows to reduce the induced voltage at the place of work on the disconnected line to values not exceeding 25 V, if the established normal mode exists on the working line. However, in the event of a short circuit occurring on a working line, the induced voltage at the place of work will significantly exceed the voltage that creates a manually controlled power source, and the residual induced voltage will significantly exceed 25 V, creating a mortal danger for workers.

The invention is aimed at solving the problem of improving the safety of work in electrical installations.

The technical result of the invention is to reduce the induced voltage at the place of work during short circuits on the working line to values less than 25 V required by safety regulations.

The technical result is achieved by the fact that in the method of compensating for the induced voltage on a disconnected overhead power line during a short circuit on a working line, the phase wires of the disconnected line are connected to the star by grounding wires at the place of work, the center of which is connected by a grounding wire to the ground loop of the line support, preliminarily determined parameters of the induced voltage source, form an autonomous source of electricity with the possibility of regulation, measure the magnitude of the induced voltage at the place of work, connect an adjustable source between the grounding circuit of the line support and grounding wires, according to the invention, the current value of the induced voltage source on the disconnected line during a short circuit on the working line is preliminarily determined, the magnitude of which forms the power value of the capacitor bank of an autonomous current source, which is constantly charged from an autonomous source of electrical energy, and during work, the current in the wire is measured, connecting m star of grounding wires with a grounding loop of the line support, the magnitude of which in real time forms a control action in the control unit, which is fed to the compensating current generation unit, at the output of which, using the charging power of the capacitor bank, an instantaneous current of equal magnitude and located in antiphase to the measured current, a compensating current is supplied to the wire connecting the star of the grounding wires to the ground loop of the line support, and the residual ennogo voltage not exceeding 25 V.

Differences from the prototype prove the novelty of the technical solution described in the claims.

The new approach allows to increase the safety of work in electrical installations, by reducing the induced voltage at the place of work both under steady-state normal conditions and with a short circuit on the working line to values less than those required by safety rules (25 V), which confirms the conformity of the declared technical solutions to the patentability condition “industrial applicability”.

From the prior art, the distinctive essential features of the proposed method, described in the claims, are unknown, which confirms their compliance with the condition of patentability "inventive step".

The invention is illustrated in the drawing, where:

in FIG. 1 is a diagram of a double-circuit overhead line with grounding of the wires of the three phases of the disconnected line at the place of work and with a connected regulated current source;

in FIG. 2 shows a line equivalent circuit in FIG. 1 for calculation according to the program in phase coordinates on a computer;

in FIG. 3 is a diagram of one portion of the line equivalent circuit of FIG. 2 with the line parameters taken into account in the calculation;

in FIG. 4 is a diagram of a current source connection for providing compensation of induced voltage at the place of work on a disconnected power line during a short circuit.

In FIG. 1 shows an overhead line 1 connected between substations 2 and 3, powered by systems 4 and 5, and an overhead line 6, disconnected from substations 2 and 3 with switches 7 and 8. The phase wires of the disconnected line 6 are connected by grounding wires 9 to a star, the center of which connected by a grounding wire 26 to the grounding circuit 10 of the line support, grounding wire 27 through a current source 11 with a remote ground electrode 12 and grounding wire 28 through a voltmeter 13 with another remote ground electrode 14.

In FIG. 2 shows the equivalent circuit of overhead lines 1 and 6 in a three-phase form for calculation on a computer according to the program in phase coordinates. The feed systems are shown in the form of three EMFs 15, of the same size and shifted relative to each other by an angle of 120 degrees. The midpoint of the EMF 15 through the resistance of the ground electrode 16 is connected to a point of zero potential. The lines are divided into sections bounded by points 17 (nodes). Each node is assigned a number. Between each two nodes of the wires there are links that are of an active-inductive nature 18. The middle point of the grounding wires 9 is connected through the resistance 19 of the grounding contour of the support 10 to a point of zero potential. The current source 11 is connected through the resistance 20 of the ground electrode 12 to a point of zero potential. The voltmeter 13 is connected through the resistance 21 of the ground electrode 14 with a point of zero potential.

In FIG. Figure 3 shows the equivalent circuit of one of the sections of the equivalent circuit of overhead lines 1 and 6 in three-phase form for calculation on a computer according to the program in phase coordinates. Here, between the nodes of the line wires, the total resistances of the wires 22 are shown. Between the wires, capacitances 23 and capacitances to earth 24 of each wire are shown. Between the wires shown mutual resistance 25.

In FIG. 4 shows a connection circuit of a compensating current source, consisting of a control unit 33 and a compensating current generating unit 35. In the circuit, the current is measured in the grounding wire 26 by the device 31 and transmitted to the measuring system 36 of the control unit 33, the current is measured in the grounding wire 27 by the device 32 and transmit it to the measuring system 36. From the measuring system 36, the signal is digitally supplied to the processor 37, then fed to the pulse-width modulation unit 38. Next, the signal is supplied to the pulse shaper 34. Using pulses 34, control signals are generated that are fed to bipolar transistors 39 of block 35. Transistors 39 instantly respond to control signals and, using the energy of the capacitor bank 29, create a compensating current in the ground wire 27. The capacitor bank 29 is constantly charged from an autonomous power source 30. In this case, compensation of the induced voltage is carried out both with steady-state normal mode and with a short circuit on a working line. At the time of a short circuit on a working line, the power source 30 is disconnected from the circuit by a switch 40.

For the double chain line in FIG. 1 according to the equivalent circuit of FIG. 2 in view of FIG. 3, with the compensating current source 11 switched off, a series of calculations according to the program in phase coordinates were performed.

For the program, the values of the complex resistances of the phase wires of the line and the interfacial complex resistances (respectively, intrinsic and mutual resistances) are determined by well-known expressions (for example, Ulyanov S.A. Electromagnetic transient processes in energy systems, Energiya publishing house, 1970, p. 293, 294).

The values of the capacitive conductivities of the phases to ground and the mutual capacitive conductivities between the phases are determined by well-known expressions (for example, A. Visyashchev. Instruments and methods for determining the location of damage on power lines, Irkutsk, textbook, ISTU publishing house, 2001). , p. 27-29).

When conducting computational experiments, short circuits were installed alternately at several points on the working line and performed:

1. grounding on a disconnected line only at the place of work;

2. grounding on a disconnected line at the place of work and at its ends,

while moving the grounding point of the wires of the disconnected line along the line for each point of the short circuit.

The results obtained made it possible to determine the calculated current of the induced voltage source and showed that in all modes for the case under consideration (short circuit on the working circuit of a two-circuit three-phase 220 kV line 200 km long), the induced voltage on the disconnected circuit exceeds the normalized (25 V). Moreover, in the case of grounding on a disconnected line at the place of work and at the ends, the induced voltage at the place of work can reach 1000 V or more, which practically leaves no chance for the working personnel to save life. In the case of grounding on a disconnected line only at the place of work, the induced voltage at the place of work reaches not more than 200 V.

To implement the method, it is proposed that the disconnected line at the ends not be earthed, which will significantly reduce the power and size of the compensating device. At the place of work, ground wires 9 are connected by phase wires 6 of the disconnected line to a star, the center of which is connected by ground wire 26 to the ground loop 10 of the line support; previously, using the mathematical model of a double-circuit line (Fig. 2 and Fig. 3), the source current value is determined induced voltage on the disconnected line 6 during a short circuit on the working line 1, the magnitude of which form the value of the power of the capacitor bank 29 of an autonomous current source, which is constantly charged from of a separate source of electric energy 30, measure the current in the wire 26 connecting the star of the grounding wires 9 with the ground loop of the support line 10, the magnitude of which in real time form a control action in the control unit 33, which is fed to the compensating current generating unit 35, the output of which Using the charging power of the capacitor bank 29, an instantaneous current equal in magnitude and in antiphase to the measured current in the wire 26 is set, compensating current is supplied through the wire 27 to the wire 26, with connecting the star of the grounding wires with the ground loop of the line support, and control the value of the residual induced voltage, not exceeding 25 V.

In this case, the residual induced voltage is automatically reduced to values significantly less than 25 V, both under steady-state normal mode and with a short circuit on a working line.

Claims (2)

1. A method of compensating for induced voltage at the site of work on an off-line overhead power line during a short circuit on a working line, in which at the site of work the phase wires of the disconnected line are connected with ground wires to a star, the center of which is connected by an ground wire to the ground loop of the line support, previously determine the parameters of the induced voltage source, form an autonomous source of electricity with the possibility of regulation, measure the magnitude of the induced voltage at the place of work, connect an adjustable source between the ground loop of the line support and ground wires, characterized in that the current value of the induced voltage source on the disconnected line is preliminarily determined during a short circuit on the working line, the magnitude of which forms the power value of the capacitor bank of an autonomous current source , which is constantly charged from an autonomous source of electrical energy, and during work, measure the current in the wire connecting the star to grounding wires with a grounding loop of the line support, the magnitude of which in real time forms a control action in the control unit, which is fed to the compensating current generation unit, at the output of which, using the charging power of the capacitor bank, an instantaneous current equal to the value and located in out of phase to the measured current, a compensating current is supplied to the wire connecting the star of the grounding wires to the ground loop of the line support, and the residual induced value is monitored voltage not exceeding 25 V. 2. The method according to p. 1, characterized in that the disconnected line is not necessarily connected at the ends with the grounding loops of the substations.

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